[cdac] Clear cached data as part of IXCLRDataProcess::Flush

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Abstractions/Target.cs

@@ -139,6 +139,10 @@ public interface IDataCache
         /// <param name="data">On return, set to the cached data value, or null if the data hasn't been cached yet.</param>
         /// <returns>True if a copy of the data is cached, or false otherwise</returns>
         bool TryGet<T>(ulong address, [NotNullWhen(true)] out T? data);
+        /// <summary>
+        /// Clear all cached data
+        /// </summary>
+        void Clear();
     }
 
     /// <summary>

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader/ContractDescriptorTarget.cs

@@ -519,6 +519,11 @@ public bool TryGet<T>(ulong address, [NotNullWhen(true)] out T? data)
 
             return false;
         }
+
+        public void Clear()
+        {
+            _readDataByAddress.Clear();
+        }
     }
 
     private readonly struct Reader(ReadFromTargetDelegate readFromTarget)

src/native/managed/cdacreader/src/Legacy/SOSDacImpl.IXCLRDataProcess.cs

@@ -14,7 +14,15 @@ namespace Microsoft.Diagnostics.DataContractReader.Legacy;
 internal sealed unsafe partial class SOSDacImpl : IXCLRDataProcess, IXCLRDataProcess2
 {
     int IXCLRDataProcess.Flush()
-        => _legacyProcess is not null ? _legacyProcess.Flush() : HResults.E_NOTIMPL;
+    {
+        _target.ProcessedData.Clear();
+
+        // As long as any part of cDAC falls back to the legacy DAC, we need to propagate the Flush call
+        if (_legacyProcess is not null)
+            return _legacyProcess.Flush();
+
+        return HResults.S_OK;
+    }
 
     int IXCLRDataProcess.StartEnumTasks(ulong* handle)
         => _legacyProcess is not null ? _legacyProcess.StartEnumTasks(handle) : HResults.E_NOTIMPL;

src/native/managed/cdacreader/tests/TestPlaceholderTarget.cs

@@ -230,19 +230,17 @@ public override Target.TypeInfo GetTypeInfo(DataType dataType)
     public override ContractRegistry Contracts => _contractRegistry;
 
     // A data cache that stores data in a dictionary and calls IData.Create to construct the data.
-    private class DefaultDataCache : Target.IDataCache
+    private sealed class DefaultDataCache : Target.IDataCache
     {
-        protected readonly Target _target;
-        protected readonly Dictionary<(ulong, Type), object?> _readDataByAddress = [];
+        private readonly Target _target;
+        private readonly Dictionary<(ulong, Type), object?> _readDataByAddress = [];
 
         public DefaultDataCache(Target target)
         {
             _target = target;
         }
 
-        public virtual T GetOrAdd<T>(TargetPointer address) where T : Data.IData<T> => DefaultGetOrAdd<T>(address);
-
-        protected T DefaultGetOrAdd<T>(TargetPointer address) where T : Data.IData<T>
+        public T GetOrAdd<T>(TargetPointer address) where T : Data.IData<T>
         {
             if (TryGet(address, out T? result))
                 return result;
@@ -258,9 +256,7 @@ protected T DefaultGetOrAdd<T>(TargetPointer address) where T : Data.IData<T>
             return result!;
         }
 
-        public virtual bool TryGet<T>(ulong address, [NotNullWhen(true)] out T? data) => DefaultTryGet<T>(address, out data);
-
-        protected bool DefaultTryGet<T>(ulong address, [NotNullWhen(true)] out T? data)
+        public bool TryGet<T>(ulong address, [NotNullWhen(true)] out T? data)
         {
             data = default;
             if (!_readDataByAddress.TryGetValue((address, typeof(T)), out object? dataObj))
@@ -273,6 +269,11 @@ protected bool DefaultTryGet<T>(ulong address, [NotNullWhen(true)] out T? data)
             }
             return false;
         }
+
+        public void Clear()
+        {
+            _readDataByAddress.Clear();
+        }
     }
 
 }